“I dont call this transit, I call this detention,” UN refugee chief Filippo Grandi told reporters in Budapest after visiting the Roszke transit zone, one of two camps built into a razor-wire fence on Hungary’s 175-kilometre (110-mile) frontier with Serbia.

Since April this year, asylum-seekers are automatically and indefinitely held at the camps — which are off-limits to journalists — during the processing of their asylum applications.

“It may take weeks, months until the end of the procedure,” said Grandi.

Hungary’s hardline anti-immigration Prime Minister Viktor Orban says the system prevents migrants with “unclear status”, and who may pose a security risk, from moving freely around the country and the EU.

But their confinement fails to meet EU standards on protection of asylum-seekers, say rights groups like Amnesty International.

“Seeking asylum is not a crime,” said Grandi.

His UNHCR body has previously warned Hungary of the likely “terrible physical and psychological impact on women, children and men who have already greatly suffered”.

On Tuesday, Grandi urged the Hungarian authorities to exempt from the rules not just unaccompanied minors under 14-years-old — who are taken to a children’s facility outside Budapest — but also those aged between 14 and 18.

He also said the authorities should allow more than the current five asylum-seekers per day into the transit zone, and that the rejection rate of applications in Hungary was too high compared to other European countries.

Since the erection of the border fences in 2015 the number of migrants entering Hungary has fallen to a trickle.

In 2015, when more than one million people landed on Europe’s shores, over 400,000 refugees and migrants crossed through Hungary.

But according to the latest UNHCR figures (August 21), just 471 asylum-seekers are now inside the EU member state.

This includes 25 people accommodated at open “reception centres”, 19 detained in asylum detention centres for “aliens” inside the country, and 427 in the two transit zones.

Hungary has also refused to take part in an EU scheme to spread up to 160,000 Syrian, Iraqi and Eritrean asylum seekers among the 28 member states.

After an EU court last week rejected Hungary’s legal challenge to the scheme Orban said that although Budapest “acknowledges” the ruling, it will not change an “immigration policy that rejects migrants”.